Domestic appliance



March 25, 1958 M. E. FRY

DOMESTIC APPLIANCE Filed Oct. 14, 1955 Fig. 2

INVENTOR. Mil/0rd 5. Fry

His Afro/hey N W V m 1 IN.

m m, m M mm m w MW wt United States. Patent DOMESTIC APPLIANCE Millard E. Fry, Dayton, Ohio, assignor to General Motors Corporation, Detroit, Mich., a corporation of Belaware Application October 14, 1955, Serial No. 540,552

2 Claims. (Cl. 219-20) This invention relates to a domestic appliance and more particularly to domestic electric ranges.

It is customary in electric range ovens to provide fixed top heats for broiling, baking and pre-heating. The practical' limitations upon such circuits often make it impossible to provide the ideal amount of heat. Also for broiling the only possible adjustment was to raise or lowerthe broiling rack or pan relative to the broiling heater.

' It is an object of my invention to provide a heating system for an oven which provides the ideal amount of top heat both for broiling and baking.

It is another object of my invention to provide an adjustment of the heating rate for broiling.

These and other objects are obtained in the form shown in the drawings in which the broil heater is controlled by an intermittently operating, user adjustable, infinite heat vibrating or pulsing type switch. A factory adjustable pulsing switch is also used to limit the amount of top heat provided by the broil heater during baking.

Further objects and advantages of the present invention will be apparent from the following description, reference being; had to the accompanying drawings, wherein a preferred form of the present invention is clearly shown.

In the drawings:

Figure 1 is a wiring diagram disclosing one, form of my invention; and,

Figure 2 is a wiring diagram disclosing a second form of my invention.

Referring now to the drawings and more particularly to Figure 1, there are shown the supply conductors L N, and L The conductor L is connected to the thermostatically operated switch contact means 20 while the supply conductor L is connected to the thermostatically operated switch contact means 22. A conductor 24 connects the conductor L to the switch contact means 26. These three switch contact means are preferably opened and closed simultaneously by an oven thermostat 27 operated in response to the temperature of the oven 28 indicated diagrammatically in Figure 1. This switch, for example, may be similar to the switch shown in the Weber Patent No. 2,389,014, issued November 13, 1945. The oven compartment preferably contains an upper broil heater 30 and a lower bake heater 32.

The contact means 20 are connected by the conductor 34 to the bake switch 36 and the broil switch 38. The broil switch 38 is connected by the conductors 40 and 42 to one terminal of the broil heater 30. The bake switch 36 is connected by the conductors 44 and 46 to one terminal of the bake heater 32. The two circuits are connected together by the conductor 48.

On the opposite side the switch contact means 22 is connected by the conductor 50 to the second broil switch 52 and the second bake switch 54. The second bake switch 54 is connected by the conductors 56 and 58 to the second terminal of the bake heater 32. For the purpose of providing a small carefully controlled top heat when the baking circuit is energized, there is provided an intermittently opening continuous vibrating or pulsing switch 60. which is closed 10% of the time by the cam 62 upon the extended shaft of an electric motor 72. The switch 60 intermittently provides a connection between the second terminal of the broil heater 30 and the conductor 64 connecting with the conductor 56. The switch 60 is kept open about of the time.

The thermostat closes the contacts 20, 22 and 26 simultaneously. For baking, the bake switches 36 and 54 are both closed contacting the conductors 34 and 50 and thus connecting the bake heater 32 directly across the supply conductors L and L for maximum input. Current also flows from the conductor 56 through the conductor 64, the continuously vibrating switch 60, the broil heater 30, and the conductors 42 and 48 to the conductor 44. The cam 62 is rotated at least 1 R. P. M. by the motor 72 to intermittently open and automatically reclose the switch 60 for such short periods that the switch 60 remains closed only about 10% of the time when connected in the circuit as thus described. This reduces the average heat output of the broil heater 3t) to provide an average amount of top heat which is reduced sulficiently to provide in conjunction with the bake heater 32 a substantially even heat within the compartment of the oven 28.

For broiling, there is provided a second intermittently operable switch 66 which is connected by the conductor 68: to the second broil switch 52. The switch 66 is intermittently opened by a cam 71) on the shaft of the elec tric motor 72. This motor 72 is connected in parallel with the pilot light 74 between the switch 26 and the neutral supply conductor N. The infinite heat switch 66 is adjusted by the screw 76 to provide a proportion of closed time varying from 55% to Thus, when the thermostat contacts 20, 22 and 26 and the broil contacts 38 and 52 are closed, the broil heater 30 will be energized at an average rate or output which may be adjusted from 55% to 100% in order to obtain exactly the desired heating rate required for the broiling operation to be performed.

Referring now more particularly to Figure 2 for the second form of the invention, the supply conductor L is connected to the thermostatically-operated switch contact means and the supply conductor L is connected to the thermostatically-operated switch contact means 122. Both switches are operated by a thermostat that is identical with thermostat 27 and which responds to the temperatures of the oven compartment that houses heating elements 136 and 132. The switch contact means 120 similarly connects to the first broil switch 138 and the first bake switch 136. The switch contact means 122 similarly connects to the second broil switch 152 and the second bake switch 154. The first broil switch 138 is connected by the conductors 144 and 146 to the left terminal of the lower bake heater 132. The first broil switch 138 is connected by the conductor to the left terminal of the upper broil heater 30. The conductor 144) is extended to connect directly with the switch contact means 121 The right terminal of the lower bake heater 132 is connected by the conductor 158 and by a tapped control resistance heater and the conductor 156 to the second bake switch 154. A thermally operable bimetal switch 160 connects the second terminal of the upper bake heater and the control resistance 155 as shown in Figure 2. The control resistance 155 is thermally associated with the thermally operable switch 160 which is normally closed when not heated.

When the bake switch means 136 and 154 and the thermostat contacts 126 and 122 are closed, current will flow through the lower bake heater 132 and the control resistance 155 to cause the heater 132 to operate at its .3 maximum capacity. The current will also how intermittently through the upper broil heater 130 under the control of the vibrating or pulsing switch 160 in the enclosure 161. The control heater 155 is likewise enclosed in the enclosure 161 in sufiicient thermal exchange relation with the intermittently opening automatically reclosable vibrat ing type switch 160 to keep the switch 161 closed in short periods about 10% and open 90% of the time to reduce the average heat output of the upper broil heater to 10%. This arrangement makes it possible to provide an ideal amount of top heat, coincidentally, with maximum heat of the lower bake heater 32 for baking.

For broiling, the switches 136 and 54 are opened and the switches 138 and 152 are closed. The switch 152 is connected by the conductor 1&8 to a tap selector 170 which connects selectively to the taps 172 and 17 5 which connect with the opposite ends of the control resistance 155.. The tap selector 170 also connects to the intermediate taps I76 and 1755 of the control resistance 155. in this broil arrangement as many broil speeds can therefore be obtained from the broil heater 130 as there are taps provided for the control resistance 155.

In each or" these forms, fast preheating of each of the ovens may be obtained by closing all of the switches and by adjusting the selector for the intermittently operable switches to be closed 100% of the time.

Mule the form of embodiment of the invention as herein disclosed constitutes a preferred form, it is to be understood that other forms might be adopted, as may come within the scope of the claims which follow.

What is claimed is as follows:

1. An electric heating circuit for an electrically heated oven comprising, an electric heating element located in the upper portion of said oven, an energizing electrical circuit for said heating element adapted to be connected with input power supply leads, a thermostatically operated switch connected in series with said energizing circuit and heating element for controlling the energization of said heating element in response to temperatures within the oven, a pulsing switch connected in series circuit relationship with said energizing circuit, heating element, and thermostatically operated switch, said pulsing switch opening and closing periodically and having variable predetermined ratios of closed time to open time, and means for varying the ratio of closed time to open time of said pulsing switch independently of said thermostatically operated switch and irrespective of the temperature setting of said thermostatically operated switch, whereby said heating element is deenergized whenever said thermostatically operated switch is open and the heating effect heating element is controlled by said pulsing switch when said thermostatically operated switch is closed and means for adjusting said thermostatically operated switch independently of said pulsing switch.

An electric heating circuit for an electrically heated oven lg, an upper electrical broiling heating element in said oven, an energizing circuit adapted to be connected with input supply leads for energizing said broiling element and including lower power output terminals adapted to energize an electrical heating element, a thermostatically operated switch connected in series with said energizing circuit for controlling the energization of said broiling element in response to temperatures within the oven, a pulsing switch connected in series circuit relationship with said energizing circuit, broiling element, and thermostatically operated switch, said pulsing switch open ing and closing periodically and having variable predetermined ratios of closed time to open time, and means for varying the ratio of closed time to open time of said pulsing switch independently of said thermostatically operated switch and irrespective of the temperature setting of said thermostatically operated switch, whereby said broiling element is deenergized whenever said thermostatically operated switch is open and the heating effect of said broiling element is controlled by said pulsing switch when said thermostatically operated switch is closed and means for adjusting said thermostatically operated switch independently of said pulsing switch.

References Cited in the file of this patent UNITED STATES PATENTS Schauer Apr. 23, 1957; 

